I used it for 6 weeks. My cat is not a picky eater and ate it up on his regular food. But I saw no difference.
The reason for 4 stars - I quickly received a response on how to return and get a refund. I got my refund quickly.
It seems like a lot of pets benefit from this. With their great refund process, it is worth trying it out to see if it works for your dog/cat.
Bottom Line: Yes, I would recommend this to a friend